Well I have a couple of theories as to how to defeat this device:
1) Cover yourself with something that absorbs the radiation. Obviously they tried sunblock and street clothes, neither of which absorbed very well. What did we learn from the report? Skin absorbs very well - ie leather is probably a good insulator. So construct a cape and hood, or a complete leather outfit. When your face starts to burn, cover up. Seeing is the only challenge. But it might be possible to find goggles which will take care of that problem. I'm sure they make laser safety goggles for every wavelength.
2) Faraday cages can be very effective at blocking some radiation types. This is how your microwave contains the radiation and keeps you from getting nuked along with your popcorn. Chainmail? A chicken wire box? The only challenge is that you have to ground it. A nearby lamp post or parking meter or something might be good. (and an extension cord if you still want mobility)
If they really do use the goodbye weapon for perimeter defense - leaving it on all the time near an embassy or something, it would be easy to test various protectants by wandering in and out of the field and see what happens.